Soybean yields in the midsouthern states of Arkansas, Louisiana, and Mississippi have reached respectable levels (Table 1). During the 2001–2005 period, average yields ranged from 33.4 bu/acre (Louisiana) to 35.7 bu/acre (Mississippi). These yields are 8.1 to 11.3 bu/acre greater than the average from the 1989–1993 period, when average yields in the three states ranged from 24.4 bu/acre (Mississippi) to 27.4 bu/acre (Arkansas).
It is impossible to designate any one factor or set of factors as the primary cause of this yield improvement. However, there are several documented changes in management that have coincided with the increased yields.
First, early planting of early-maturing varieties on a significant acreage was first documented in 1994. By the 2001–2005 period, early planting averaged 25%, 39%, and 68% of the soybean acreage in Arkansas, Louisiana, and Mississippi, respectively, compared to less than 3% in the 1989–1993 period.
Second, use of adapted MG IV varieties became important in the mid-1990s with the release and subsequent use of DP 3478 on a large acreage. This was the first truly productive variety adapted for use in the early soybean production system. It has since been supplanted by a progression of adapted, high-yielding MG IV varieties that are maintaining a continued genetic improvement in yield potential.
Third, glyphosate-resistant varieties reached an average usage of over 75% in the midsouth region during the 2001–2005 period. In Arkansas and Mississippi in 2005, they were used on 92% and 96% of the planted acreage, respectively (data for Louisiana are not available). These biotechnology varieties allowed more efficient and effective weed control, thereby reducing the impact of poor weed management on yields.
Finally, new products and technology have been forthcoming. Effective seed treatments ensure a stand in early plantings. Recently labeled foliar fungicides ensure that yield potential is protected when weather conditions during seed development and maturation promote the development of seedrot pathogens that will reduce quality and yield. Adoption of improved irrigation initiation and scheduling guidelines has increased the magnitude and consistency of irrigated yields.
Soybean acreage in the midsouth may increase in 2006. The impact of this increased acreage will be magnified if the practices that have been associated with increased yields over the last five years are used on these added acres.
Soybean yield increases in the midsouth will continue in the foreseeable future as newer, proven technology is adopted on an increasingly larger acreage.
Table 1. Midsouth soybean yields (bu/acre) during the 1989-1993 and 2001-2005 periods.